Herbicidal use of substituted phenyl phosphinic acids

ABSTRACT

Substituted phenyl phosphinic acids and derivatives thereof exhibit herbicidal activity, especially when used to control broadleaf weeds.

This application is a continuation-in-part of Ser. No. 620,982 filed Oct. 9, 1975, now abandoned.

This invention relates to substituted phenyl phosphinic acids and derivatives thereof and their use as herbicides and in herbicidal compositions. More particularly, this invention relates to the herbicidal use of substituted phenyl phosphinic acids and derivatives thereof having the formula ##STR1## wherein R is selected from the group consisting of primary and secondary alkyl and trihalomethyl; R₁ is selected from the group consisting of hydrogen, primary and secondary alkyl, ammonium, alkyl ammonium, and phenyl substituted by halo, lower alkoxy, nitro and trifluoromethyl; and X, Y and Z are independently selected from the group consisting of hydroxy, halo, trihalomethyl, amino, primary and secondary alkyl, lower alkoxy, and thioalkyl, and each n is independently zero or one.

By the term "lower alkoxy" is meant those alkoxy groups which contain from one to three carbon atoms, inclusive.

In accordance with the present invention, the following illustrative compounds have been found to be useful as herbicides:

A 2-methoxy-5-bromophenyl methyl phosphinic acid

B o-anisyl methyl phosphinic acid, isopropylamine salt

C o-anisyl methyl phosphinic acid, ammonium salt

D 2,4-dimethoxy-phenyl methyl phosphinic acid

E o-[N-methylamino]phenyl methyl phosphinic acid

F 2-methoxy-4,5-dimethylphenyl methyl phosphinic acid

G 2,4-dimethoxy-3-methylphenyl methyl phosphinic acid

H o-hydroxyphenyl methyl phosphinic acid, ammonium salt

I p-anisyl methyl phosphinic acid, isopropyl amine salt

J p-anisyl isopropyl phosphinic acid, ammonium salt

K o-anisyl trichloromethyl phosphinic acid, diethyl amine salt

L o-ethoxyphenyl methyl phosphinic acid

M o-aminophenyl methyl phosphinic acid, ethyl ester

N o-ethoxyphenyl methyl phosphinic acid, diethyl amine salt

O o-trifluoromethyl phenyl methyl phosphinic acid, ethyl ester

P 2,4-dimethoxyphenyl ethyl phosphinic acid

Q 4-methoxy-3-methylphenyl methyl phosphinic acid

R m-trifluoromethyl phenyl methyl phosphinic acid, ammonium salt

S o-anisyl ethyl phosphinic acid

T o-anisyl ethyl phosphinic acid, isopropyl amine salt

U 2-methoxy-4-isopropyl phenyl methyl phosphinic acid

V o-anisyl methyl phosphinic acid

W o-anisyl methyl phosphinic acid, 2,4-dichlorophenyl ester

X o-anisyl methyl phosphinic acid, m-trifluoromethyl phenyl ester

Y o-anisyl methyl phosphinic acid, o'-anisyl ester

Z o-anisyl methylphosphinic acid, p-nitrophenyl ester

A' o-anisyl-isopropyl phosphinic acid

B' p-chlorophenyl-methyl phosphinic acid

C' 2,5-dichlorophenyl methyl phosphinic acid

D' 3,5-dichloro-2-methoxyphenyl methyl phosphinic acid

E' o-thioanisyl methyl phosphinic acid

Generally, the phosphinic acids and their derivatives of the invention are prepared in accordance with the procedure disclosed by U.S. Pat. No. 3,992,273. The compounds are prepared via a photolysis reaction in accordance with the following reaction scheme: ##STR2##

Other known procedures may be utilized to prepare the compounds of the invention. For example, substituted aryldichlorophosphines may be reacted with lower alkanols in the presence of a base. After filtering, the filtrate is treated with an alkyl halide, preferably an alkyl iodide, to yield the phosphinic compound desired. This procedure may be summarized by the following reation scheme: ##STR3## Another approach to preparing the phosphinic compounds of the invention requires the use of an aryl Grignard reagent and dialkylclorophosphite. Briefly, the reaction involved may be illustrated as follows: ##STR4##

In accordance with the invention, the compounds of formula I are useful as herbicides. Table 1 summarizes results of tests conducted to determine the pre-emergent as well as the post-emergent herbicidal activity of the compounds. The pre-emergent test was conducted as follows:

A good grade of top soil was placed in aluminum pans and compacted to a depth of three-eighths to one-half inch from the top of the pan. On the top of the soil was placed a predetermined number of seeds or vegetative propagules of various plant species. The soil required to level fill the pans after seeding or adding vegetative propagules was weighed into a pan. A known amount of the active ingredient applied in a solvent or as a wettable powder and the soil were thoroughly mixed, and used as a cover layer for prepared pans. After treatment the pans were moved into a greenhouse bench where they were watered from below as needed to give adequate moisture for germination and growth.

Unless noted otherwise, approximately 28 days after seeding and treating, the plants were observed and the results recorded. The herbicidal rating was obtained by means of a fixed scale based on the average percent germination of each seed lot. The ratings are defined as follows:

    ______________________________________                                                % Control  Rating                                                       ______________________________________                                                 0-24      0                                                                   25-49      1                                                                   50-74      2                                                                    75-100    3                                                            ______________________________________                                    

The post-emergent tests were conducted as follows. The active ingredients were applied in spray form to two or three-week old specimens of various plant species. The spray, a solution or wettable powder suspension containing the appropriate rate of active ingredient to give the desired test rate and a surfactant, is applied to the plants. The treated plants are placed in a greenhouse and unless otherwise noted approximately 4 weeks later the effects are observed and recorded. The results are shown in Table 1 in which the post-emergent herbicidal activity index is as follows:______________________________________% Control Rating______________________________________ 0-24 024-49 150-74 275-99 3100 4______________________________________

The plant species utilized in these tests are identified by letter in accordance with the following legend:______________________________________A Canada Thistle G NutsedgeB Cocklebur H bromus tectorumC Velvetleaf I JohnsongrassD Morningglory J QuackgrassE Lambsquarter K Barnyard grassF Smartweed______________________________________

                                      TABLE 1                                      __________________________________________________________________________     Rate                               Rate                                        1lb/Acre                           1lb/Acre                                    (kilos/      Pre-Emergent          (kilos/                                                                              Post-Emergent                         Compound                                                                             hectare)                                                                              A B C D E F G H I J K hectare)                                                                             A B C D E F G H I J K                 __________________________________________________________________________     A                                   4                                                                               (4.48)                                                                             0 2 1 2 0 0 0 0 0 0 0                 B      5 (5.60)                                                                             3 1 2 3 3 3 0 0 0 0 0  4                                                                               (4.48)                                                                             0 2 2       3                                                                              3                                                                              0                                                                              0 0 0 0 0                 C      5 (5.60)                                                                             3 1 2 3 2 0 0 0 0 0 0  4                                                                               (4.48)                                                                             1 2 2       2                                                                              1                                                                              0                                                                              0 0 0 0 0                 D      5 (5.60)                                                                             0 0 1 2 1 3 0 0 3 0 0  4                                                                               (4.48)                                                                             0 1 2       2                                                                              1                                                                              0                                                                              0 0 0 0 0                 E                                  10                                                                               (11.2)                                                                             0 1 0       2                                                                              2                                                                              0                                                                              1 0 0 0 0                 F      5 (5.60)                                                                             0 --                                                                               2 2 1 --                                                                               0 0 0 0 0  4                                                                               (4.48)                                                                             1 2 2       3                                                                              2                                                                              0                                                                              0 0 0 0 0                 G                                  10                                                                               (11.2)                                                                             1 2 2       1                                                                              1                                                                              0                                                                              0 0 0 0 0                 H                                  10                                                                               (11.2)                                                                             0 2 0       2                                                                              0                                                                              0                                                                              0 0 0 0 0                 I     *10                                                                               (11.2)                                                                             3 0 0 0 0 --                                                                               0 0 0 0 0 10                                                                               (11.2)                                                                             0 0 0       1                                                                              1                                                                              --                                                                             0 0 0 0 0                 J                                  10                                                                               (11.2)                                                                             0 0 1       1                                                                              1                                                                              --                                                                             0 0 0 0 0                 K     *10                                                                               (11.2)                                                                             0 0 0 0 0 --                                                                               0 0 3 0 0                                             L      10                                                                               (11.2)                                                                             1 0 0 0 1 --                                                                               0 0 0 0 0 10                                                                               (11.2)                                                                             0 0 0       2                                                                              1                                                                              --                                                                             0 0 0 0 0                 M                                  10                                                                               (11.2)                                                                             1 1 0       0                                                                              1                                                                              --                                                                             0 0 0 0 0                 N                                  10                                                                               (11.2)                                                                             2 2 1       2                                                                              1                                                                              --                                                                             0 0 0 0 0                 O                                  10                                                                               (11.2)                                                                             4 0 0       1                                                                              0                                                                              0                                                                              0 0 0 0 0                 P                                  10                                                                               (11.2)                                                                             2 1 1       3                                                                              1                                                                              --                                                                             0 0 0 0 0                 Q                                  10                                                                               (11.2)                                                                             0 0 0       2                                                                              1                                                                              --                                                                             0 0 0 0 0                 R                                  10                                                                               (11.2)                                                                             1 2 1       2                                                                              1                                                                              --                                                                             0 0 0 0 0                 S      10                                                                               (11.2)                                                                             1 1 2 3 2 2 0 0 0 0 0 10                                                                               (11.2)                                                                             1 2 2       3                                                                              2                                                                              --                                                                             0 0 0 0 0                 T      5 (5.60)                                                                             0 1 2 2 0 --                                                                               0 0 0 0 0 10                                                                               (11.2)                                                                             1 1 3       3                                                                              3                                                                              --                                                                             0 0 1 0 0                 U                                  10                                                                               (11.2)                                                                             1 2 1       2                                                                              1                                                                              0                                                                              0 0 0 0 0                 V                                   4                                                                               (4.48)                                                                             0 2 2       3                                                                              2                                                                              0                                                                              0 0 0 0 0                 W                                  10                                                                               (11.2)                                                                             0 1 1       3                                                                              4                                                                              1                                                                              0 0 0 0 0                 X                                  10                                                                               (11.2)                                                                             2 2 1       2                                                                              1                                                                              1                                                                              0 0 0 0 0                 Y                                  *10                                                                              (11.2)                                                                             0 0 1       1                                                                              2                                                                              0                                                                              0 0 0 0 0                 Z                                  10                                                                               (11.2)                                                                             0 --                                                                               1       2                                                                              4                                                                              0                                                                              0 0 0 0 0                  A'                                10                                                                               (11.2)                                                                             0 2 2       3                                                                              1                                                                              0                                                                              0 0 0 0                    B'    10                                                                               (11.2)                                                                             3 1 1 2 1 0 0 0 0 0 0 10                                                                               (11.2)                                                                             1 2 2       3                                                                              1                                                                              1                                                                              0 0 0 0 0                  C'                                10                                                                               (11.2)                                                                             0 1 0       2                                                                              1                                                                              0                                                                              0 0 0 0 0                  D'                                *10                                                                              (11.2)                                                                             1 1 1       2                                                                              1                                                                              0                                                                              0 0 0 0 1                  E'                                *10                                                                              (11.2)                                                                             1 2 1       2                                                                              1                                                                              0                                                                              0 0 0 0 0                 __________________________________________________________________________      *Plants observed 14 days subsequent to treatment.                        

In addition, tests were conducted to determine if the compounds were selective in nature. To determine this, the compounds of the invention were applied in accordance with the above test procedures to pans containing the following plant species:______________________________________Soybean Hemp SesbaniaSugarbeet LambsquarterWheat SmartweedRice VelvetleafSorghum bromus tectorumCocklebur Panicum Spp.Wild Buckwheat Barnyard grassMorningglory Crabgrass______________________________________

Table 2 illustrates the results obtained by the pre-emergent test while Table 3 illustrates the results obtained by the post-emergent test.

                                      TABLE 2                                      __________________________________________________________________________     Plant Species                                                                  Rate       Broadleaf  Narrow-leaf                                              Compound                                                                             lb/Acre                                                                             Soybean                                                                             Sugarbeet                                                                            Wheat                                                                              Rice                                                                              Sorghum                                           __________________________________________________________________________     B     1/4  1    0     0   0  0                                                       1    3    1     1   0  0                                                       1    2    0     0   0  --                                                      4    2    0     0   0  --                                                C     1    2    1     0   0  --                                                      4    2    0     0   0  --                                                 P*   5    0    0     0   0  0                                                 S     1    2    0     0   0  0                                                       5    3    1     0   0  0                                                 T     1    2    1     0   0  0                                                       5    3    1     0   0  0                                                 __________________________________________________________________________                Broadleaf                        Narrow-leaf                              Rate Cock-                                                                              Wild  Morning-                                                                            Hemp Lambs-                                                                             Smart-                                                                             Velvet-                                                                             Downy                                                                              Panicum                                                                             Barnyard                                                                             Crab-               Compound                                                                             lb/Acre                                                                             lebur                                                                              Buckwheat                                                                            glory                                                                               Sesbania                                                                            quarter                                                                            weed                                                                               leaf Brome                                                                              Spp. Grass                                                                               grass                __________________________________________________________________________     B     1/4  0   2     1    0    1   --  1    0   0    0    0                          1    1   2     3    1    1   0   1    0   0    0    0                          1    1   1     2    0    2   --  2    0   0    0    0                          4    1   2     3    0    2   1   2    0   0    0    0                    C     1    1   2     2    0    2   --  1    0   0    0    0                          4    1   2     3    0    2   --  2    0   0    0    0                     P*   5    0   1     1    0    0   --  1    0   0    0    0                    S     1    0   2     3    0    2   0   2    0   0    0    0                          5    1   2     3    0    3   2   3    0   0    0    1                    T     1    0   2     2    0    1   0   2    0   0    0    0                          5    2   2     3    1    2   1   2    0   0    0    0                    __________________________________________________________________________      *Observed after approximately 14 days.                                   

                                      TABLE 3                                      __________________________________________________________________________     Plant Species                                                                  Rate       Broadleaf  Narrow-leaf                                              Compound                                                                             lb/Acre                                                                             Soybean                                                                             Sugarbeet                                                                            Wheat                                                                              Rice                                                                              Sorghum                                           __________________________________________________________________________     B     1    3    1     1   1  1                                                 P     4    1    0     0   0  0                                                 S     1    3    1     1   0  0                                                       4    3    2     1   1  1                                                 T     1    3    2     1   0  0                                                       4    4    3     1   1  1                                                 V     1    3    2     1   1  0                                                 W     1    2    1     0   0  0                                                  A'   4    2    1     0   0  0                                                 __________________________________________________________________________                Broadleaf                        Narrow-leaf                              Rate Cock-                                                                              Wild  Morning-                                                                            Hemp Lambs-                                                                             Smart-                                                                             Velvet-                                                                             Downy                                                                              Panicum                                                                             Barnyard                                                                             Crab-               Compound                                                                             lb/Acre                                                                             lebur                                                                              Buckwheat                                                                            glory                                                                               Sesbania                                                                            quarter                                                                            weed                                                                               leaf Brome                                                                              Spp. Grass                                                                               grass                __________________________________________________________________________     B     1    2   2     3    0    3   --  1    0   0    0    0                    P     4    0   2     3    0    2   --  2    0   0    0    0                    S     1    2   3     3    0    2   1   2    0   0    0    0                          4    2   3     3    1    2   1   2    0   0    0    0                    T     1    2   3     3    0    4   2   2    0   0    0    0                          4    2   4     4    1    --  3   3    0   0    0    0                    V     1    1   2     3    0    1   1   1    2   0    0    0                    W     1    1   2     2    0    1   0   1    0   0    0    0                     A'   4    1   3     3    0    3   1   2    0   0    0    0                    __________________________________________________________________________

The data set forth in the foregoing tables clearly illustrate that the compounds of the present invention are effective herbicides and are particularly useful in selectively controlling broadleaf weeds in the presence of narrowleaf plants especially wheat, rice and sorghum as well as other narrowleaf plants. As is apparent from the foregoing tables, those compounds in which R is selected from the group consisting of primary and secondary alkyl are preferred.

Most preferred are those compounds in which R is a primary or secondary alkyl having from 1 to 8 carbon atoms especially methyl. R₁ may preferably be hydrogen and X, Y, and Z are preferably selected from the group consisting of primary and secondary alkyl, lower alkoxy and trihalomethyl. It is most preferred that X be methoxy at the 2 position on the benzene nucleus.

For the sake of brevity and simplicity, the term "active ingredient" has been used herein and is used hereinafter to describe the phosphinic compounds in Formula I.

In practicing the herbicidal methods of this invention, the active ingredients can be used alone or in combination with a material referred to in the art as an adjuvant in liquid or solid form. Herbicidal formulations are prepared by admixing the active ingredient with an adjuvant including diluents, extenders, carriers and conditioning agents to provide compositions in the form of finely divided particulate solids, granules, pellets, solutions, dispersions or emulsions. Thus, the active ingredient can be used with an adjuvant such as a finely divided particulate solid, a liquid of organic origin, water, a wetting agent, dispersing agent, an emulsifying agent or any suitable combination of these. The herbicidal formulations usually contain from about 0.01 to about 99 percent by weight of active ingredient.

Typical finely divided solid carriers and inert solid extenders which can be used with the active ingredients include for example, the talcs, natural and synthetic clays (e.g. kaolinites and attapulgite), pumice, silica, synthetic calcium and magnesium silicates, diatomaceous earth, quartz, Fuller's earth, salt, sulfur, powdered cork, powdered wood, ground corn cobs, walnut flour, chalk, tobacco dust, charcoal, volcanic ash, cottonseed hulls, wheat flour, soybean flour, tripoli and the like. Typical liquid diluents include for example: petroleum fractions such as kerosene, hexane, xylene, benzene, Diesel oil, toluene, acetone, ethylene dichloride, Stoddard solvent, alcohols such as propanol, glycols and the like.

Herbicidal formulations, particularly liquids and wettable particles, usually contain as a conditioning agent one or more surface-active agents in amounts sufficient to render a given composition readily dispersible in water or in oil. By the term "surface-active agent" it is understood that wetting agents, dispersing agents, suspending agents and emulsifying agents are included therein.

Specific surface-active agents which can be used in the herbicidal formulations of this invention are set out, for example, in Searle U.S. Pat. Nos. 2,426,417; Todd 2,655,447; Jones 2,412,510 and Lenher 2,139,276. In general, less than 50 parts by weight of the surface-active agent is present per 100 parts by weight of phytotoxic formulation.

Preferred wetting agents are alkyl benzene and alkyl naphthalene sulfonates, sulfated fatty alcohols, amines or acid amides, long chain acid esters of sodium isothionate, esters of sodium sulfosuccinate, sulfated or sulfonated fatty acid esters, petroleum sulfonates, sulfonated vegetable oils, polyoxyethylene derivatives of alkylphenols (particularly isooctylphenyl and nonylphenyl) and polyoxyethylene derivatives of the mono-higher fatty esters of hexitol anhydrides (e.g. sorbitan). Preferred dispersants are methyl cellulose, polyvinyl alcohol, sodium lignin sulfonates, polymeric alkyl naphthalene sulfonates, sodium naphthalene sulfonate, polymethylene bisnaphthalenesulfonate and sodium N-methyl-N-(long chain acid) laurates.

Wettable powder formulations usually contain from about 5 to about 95 parts by weight of active ingredient, from about 0.25 to 25 parts by weight of wetting agent, from about 0.25 to 25 parts by weight of dispersant and from 4.5 to about 94.5 parts by weight of inert solid extender, all parts being by weight of the total formulation. Where required, from about 0.1 to 2.0 parts by weight of the solid inert extender can be replaced by a corrosion inhibitor or anti-foaming agent or both.

Aqueous suspensions can be prepared by mixing together and grinding an aqueous slurry of water-insoluble active ingredient in the presence of dispersing agents to obtain a concentrated slurry of very finely divided particles. The resulting concentrated aqueous suspension is characterized by its extremely small particle size, so that when diluted and sprayed coverage is very uniform.

Dusts are dense finely divided particulate formulations which are intended for application to the soil in dry form. Dusts are characterized by their free-flowing and rapid settling properties so that they are not readily wind-borne to areas where they are of no value. Dusts contain primarily an active ingredient and a dense, free-flowing finely divided particulate extender. However, their performance is sometimes aided by the inclusion of a wetting agent such as those listed hereinbefore under wettable powder compositions and convenience is manufacture frequently demands the inclusion of an inert, absorptive grinding aid. Suitable classes of grinding aids are natural clays, diatomaceous earth and synthetic minerals derived from silica and silicate. Preferred grinding aids include attapulgite clay, diatomaceous silica, synthetic fine silica and synthetic calcium and magnesium silicates.

The inert finely divided solid extender for the dusts can be either of vegetable or mineral origin. The solid extenders are characterized by possessing relatively low surface areas and are poor in liquid absorption. Suitable inert solid extenders for herbicidal dusts include micaceous talcs, pyrophyllite, dense kaolin clays, ground calcium phosphate rock and phyllite, and tobacco dust. The dusts usually contain from about 0.5 to 95 parts active ingredient, 0 to 50 parts grinding aid, 0 to 50 parts wetting agent and 5 to 99.5 parts dense solid extender, all parts being by weight and based on the total weight of the dust.

The wettable powders described above may also be used in the preparation of dusts. While such wettable powders could be used directly in dust form, it is more advantageous to dilute them by blending with the dense dust diluent. In this manner, dispersing agents, corrosion inhibitors, and anti-foam agents may also be found as components of a dust.

Emulsifiable oil formulations are usually solutions of active ingredient in water-immiscible or partially water-immiscible solvents together with a surface-active agent. Suitable solvents for the active ingredient of this invention include hydrocarbons and water-immiscible ethers, esters or ketones. Suitable surface-active agents are anionic, cationic and nonionic such as alkyl aryl polyethoxy alcohols, polyethylene sorbitol or sorbitan fatty acid esters, polyethylene glycol fatty esters, fatty alkyllol amide condensates, amine salts of fatty alcohol sulfates together with long chain alcohols and oil soluble petroleum sulfonates or mixtures thereof. The emulsifiable oil formulations generally contain from about 5 to 95 parts active ingredient, about 1 to 50 parts surface active agent and about 4 to 94 parts solvent, all parts being by weight based on the total weight of the emulsifiable oil.

Granules are physically stable particulate formulations comprising active ingredient adhering to or distributed through a basic matrix of an inert, finely divided particulate extender. In order to aid leaching of the active ingredient from the particulate, a surface active agent such as those listed hereinbefore under wettable powders can be present in the composition. Natural clays, pyrophyllites, illite and vermiculite are examples of operable classes of particulate mineral extenders. The preferred extenders are the porous, absorptive, preformed particles such as preformed and screened particulate attapulgite or heat expanded, particulate vermiculite, and the finely divided clays such as kaolin clays, hydrated attapulgite or bentonitic clays. These extenders are sprayed or blended with the active ingredient to form the herbicidal formulations.

The mineral particles which are used in the herbicidal formulations usually have a size range of 10 to 100 mesh, but preferably such that a large majority of the particles have from 14 to 60 mesh with the optimum size being from 20 to 40 mesh. Clay having substantially all particles between 14 and 80 mesh and at least about 80 percent between 20 and 40 mesh is particularly preferred for use in the herbicidal formulations. The term "mesh" as used herein means U.S. Sieve Series.

The granular herbicidal formulations generally contain from about 5 parts to about 30 parts by weight of active ingredient per 100 parts by weight of clay and 0 to about 5 parts by weight of surface-active agent per 100 parts by weight of particulate clay. The preferred granular formulations contain from about 10 parts to about 25 parts by weight of active ingredient per 100 parts by weight of clay.

The herbicidal formulations can also contain other additaments, for example fertilizers, plant growth regulants, pesticides and the like used as adjuvant or in combination with any of the above-described adjuvants.

When operating in accordance with the present invention, effective amounts of the active ingredients are dispersed in or on soil or plant growth media and/or applied to above ground portions of plants in any convenient fashion. Application to the soil or growth media can be carried out by simply mixing with the soil, by applying to the surface of the soil and thereafter dragging or discing into the soil to the desired depth, or by employing a liquid carrier to accomplish the penetration and impregnation. The application of liquid and particulate solid herbicidal formulations to the surface of soil or to above ground portions of plants can be carried out by conventional methods, e.g. power dusters, boom and hand sprayers and spray dusters. The formulations can also be applied from airplanes as a dust or a spray because of their effectiveness at low dosages. In a further method, the distribution of the active ingredients in soil can be carried out by admixture with the water employed to irrigate the soil. In such procedures, the amount of water can be varied with the porosity and water holding capacity of the soil to obtain the desired depth of distribution of the active ingredients.

The application of an effective amount of the active ingredients of this invention to the soil or growth media and/or plant is very important for the practice of one embodiment of the present invention. The exact amount of active ingredient to be employed is dependent upon such factors as the plant species and stage of development thereof, the specific soil and depth at which the active ingredients are distributed in the soil and the amount of rainfall as well as the specific active ingredient employed. In foliar treatment for the modification of vegetative growth, the active ingredients are applied in amounts greater than one pound and up to about 25 or more pounds per acre. In applications to soil for the modification of the germination or subsequent growth of seeds or vegetative propagules or growth of established vegetation, the active ingredients are applied in amounts from above 1 to about 50 or more pounds per acre. It is believed that one skilled in the art can readily determine from the teachings of this specification the general procedure for any application.

In summary, in general the active ingredients may be formulated with the active ingredient in minor or major proportions in accordance with the table below:______________________________________ Concentration ofType of Formulation Active Ingredient______________________________________1. Granules of relatively 5 to 50% large particle size2. Powdery dusts 2 to 90%3. Wettable powders 2 to 90%4. Emulsifiable concentrates 5 to 95%5. Solutions .01 to 95%6. One of the less common types .01 to 95% of formulations depending on the desired mode of appli- cation______________________________________

Although this invention has been described with respect to specific modifications, the details thereof are not to be construed as limitations, for it will be apparent that various equivalents, changes and modifications may be resorted to without departing from the spirit and scope thereof and it is understood that such equivalent embodiments are intended to be included herein. 

What is claimed is:
 1. A method of selectively preventing the growth of undesirable broadleaf plants in the presence of narrowleaf plants which comprises applying to the plant system a herbicidally effective amount of a compound having the formula ##STR5## wherein R is selected from the group consisting of primary and secondary alkyl and trihalomethyl; R₁ is selected from the group consisting of hydrogen, primary and secondary alkyl, ammonium, alkyl ammonium and phenyl substituted by halo, lower alkoxy, nitro and trifluoromethyl; and X, Y and Z are independently selected from the group consisting of hydroxy, halo, trihalomethyl, amino, primary and secondary alkyl, lower alkoxy and thioalkyl; and each n is independently zero or one.
 2. A method according to claim 1 wherein R is selected from the group consisting of primary and secondary alkyl.
 3. A method according to claim 2 wherein R is methyl.
 4. A method according to claim 2 wherein R₁ is hydrogen.
 5. A method according to claim 4 wherein X is methoxy at the 2 position of the benzene nucleus.
 6. A method of selectively preventing the growth of undesirable broadleaf plants in the presence of narrowleaf plants which comprises applying to the plant system a herbicidally effective amount of a compound having the formula ##STR6## wherein R is selected from the group consisting of primary and secondary alkyl; R₁ is selected from the group consisting of hydrogen, primary and secondary alkyl, ammonium, alkyl ammonium, and phenyl substituted by halo, lower alkoxy, nitro and trifluoromethyl; and X, Y and Z are independently selected from the group consisting of primary and secondary alkyl, lower alkoxy and trihalomethyl; and each n is independently zero or one.
 7. A method according to claim 1 wherein said narrowleaf plants are wheat, rice and sorghum.
 8. A method according to claim 6 wherein said narrowleaf plants are wheat, rice and sorghum. 